Plane & Pilot
Tuesday, February 9, 2010

Getting Ready For NextGen

The controllers are as crucial as the automation

Tyndall RAPCON is a U.S. Air Force approach facility; it lacks displays for controllers that show weather intensity. Instead, when a controller begins a shift, he or she receives initial weather information from the watch supervisor and also from looking at a wall display that loops a weather radar picture from The wall display doesn’t provide close-up coverage of the Tyndall/Panama City area. On the day of the accident, weather at Panama City was VFR, but there were thunderstorms in the vicinity. The first RAPCON controller who handled the flight noted the planned route would take the airplane through an area of weather. After the airplane started descending to 6,000 feet, the controller started a handoff to the Panama sector of the RAPCON. The first controller had no discussions with the Panama controllers about weather information.

When the pilot checked in with the Panama sector, that controller didn’t know if the pilot had been advised of the weather ahead. The airplane was still proceeding direct to PFN, descending to 6,000 feet. The radar controller issued a “pilot’s discretion” descent to 3,000 feet, which the pilot acknowledged. The controller stated that when he took the handoff, the airplane was already on the eastern edge of weather that was about 10 miles deep. The pilot didn’t ask about weather or deviations. The airplane strip used by the controller showed that the pilot had received the ATIS information, but there were no other notations about weather. He wasn’t sure if the airplane actually was in the precipitation area at the time. When he transmitted that radar contact was lost and received no response when asking the pilot for a position report, he initially thought the pilot had gone off frequency on his own.

An NTSB investigation showed that the weather along and near the route of flight included moderate and extreme cells. A controller’s assistant explained that Tyndall controllers communicate with Eglin Air Force Base controllers to obtain weather information because Eglin has better weather displays, but he wasn’t sure what they looked like. Another assistant said he didn’t like NEXRAD displays, which showed only three weather intensities. He was aware that cyan is used to depict the worst weather, but was unable to describe the appearance of the other two weather intensities (royal blue for least intense and checkered cyan for moderate). Investigation showed that the Tallahassee and North Florida NEXRAD weather radars were out of service at the time of the accident. They are among eight radar sites providing controllers with part of their weather coverage in the accident area. Tyndall RAPCON’s manager told investigators that when he learned of the accident, he became concerned about what the controllers might have been seeing or not seeing at the time of the accident. Pictures showing a fast-growing area of weather may not necessarily have been on ATC displays. Operations managers weren’t always told that NEXRAD radars were out of service, but the manager believed that this would be useful information.

The NTSB determined that the probable cause of this accident was the pilot’s inadvertent flight into thunderstorm activity, which resulted in a loss of control, the exceeding of the airplane’s design limits and its subsequent in-flight breakup. A contributing factor was the failure of ATC to use available radar information to warn the pilot he was about to encounter moderate, heavy and extreme precipitation along his route of flight.


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